The present invention relates to a tray for transporting products and the method for its manufacturing, the tray being formed from at least one sheet of cardboard or a similar material, previously die-cut and with fold-lines defining the bottom and the sides of the tray.
At the moment different types of cardboard trays are known for the transportation of products. These well-known trays are formed from a die-cut sheet and are provided with fold-lines that define the bottom and the sides of the tray.
To be able to stack the trays, these trays present columns of polygonal, usually triangular, cross section, at their corners that keep them straightened in work position. These columns are usually formed starting from a headwall that adheres to the smaller sides of the tray.
These well-known trays have the main drawback that they occupy a considerable amount of space when they are transported empty.
To solve this problem the tray described in the utility model no. ES-U9201875 was devised, whose common features with the tray of the present invention are pointed out in the preamble of claim 1. This tray comprises a triangular column at each one of its corners and a reinforcement plate that is introduced in each one of these columns. It was thus possible to have a tray that could be transported folded, occupying a very small volume, and had sufficient rigidity to stack one box on top of another by fitting the reinforcement plate.
However, this tray presents the drawback that the reinforcing plate is not sufficient to support heavy weights. It also has the drawback that the tray has a given capacity, with no possibility of increasing it.
Furthermore, the methods for manufacturing this type of tray are carried out by shaping and gluing the parts of the tray in folded position, which has the drawback that said gluing is not very precise and has a width limit.
EP-A-0 076 883 discloses a blank of foldable sheet material, for erection into a container, which comprises a generally rectangular central portion for forming the base of the container and the panels hingedly connected along at least three edges of the central portion for erection to form side walls of the container, at least one of the panels being provided with a flap having at least one fold line which extends substantially parallel to the hinge, whereby the flap may be folded to form a load-bearing corner strut which can be located within the base of the container, when the container is erected.
GB-A-91044 discloses a tray for soft fruit, formed from a sheet of cardboard, previously die-cut and with fold-lines that define the bottom and the sides of the tray, with each one of the corners of same comprising a column of triangular cross section into which a reinforcing element of triangular cross section is inserted. One of the sides of the triangle defined in the columns has a double layer.
With the tray and the method of the invention the aforesaid drawbacks are solved, while other advantages are presented that will be described below.
The tray for the transportation of products of the invention is characterised in that said reinforcing element has a cross section equivalent to the cross section of the column, so that said reinforcing element fits inside the column.
Thanks to this characteristic a tray is provided that may be transported folded, occupying a small space and capable, moreover, of withstanding considerable weights by placing the reinforcing element in the columns.
Advantageously, the reinforcing element is formed from a sheet, with this sheet folded so that one of its sides is in contact with one of the vertexes of the polygon defined by the cross section of the reinforcing element.
According to a first embodiment, the height of the reinforcing element is substantially the same as the height of the column.
According to an alternative embodiment, the height of the reinforcing element is greater than the height of the column. It is thus easy to increase the capacity of the tray of the invention by increasing the height of the reinforcing element.
Also advantageously, each reinforcing element comprises at least one projection on its upper part that fits into a complementary cavity in the lower part of the reinforcing element when the trays are stacked, preventing the displacement of one tray with respect to another both longitudinally and transversally.
Preferably, each one of the columns includes at least one projection on its upper part that fits into a complementary cavity provided in the lower part of the tray when the trays are stacked.
According to a preferred embodiment, the reinforcing element comprises a double layer on each one of its sides.
Also according to a preferred embodiment, the reinforcing element includes three projections on its upper part, which fit into complementary cavities provided in the lower part of the reinforcing element when the trays are stacked.
Preferably, two opposing sides of the tray each include a pair of tabs which are inserted between the column and the reinforcing element. These tabs further reinforce the tray of the invention, since they prevent the ungluing of the smaller sides or headwalls. This feature is especially important because these trays are designed to transport considerable weights. It has been shown that without these tabs, the headwalls may be unglued, causing the break of the tray when the trays are transported individually.
Also preferably, the tray of the invention comprises prolongations on the sides of the tray that reinforce the column with an additional layer.
According to an alternative embodiment, the columns extend towards two opposite sides of the tray, reinforcing said opposite sides with a double additional layer.
The present invention also relates to a method for manufacturing trays for transporting products starting with at least one sheet of cardboard or similar material, characterised in that it includes the following stages:
die-cutting of said cardboard sheet;
formation of fold-lines on said sheet, defining a pair of side walls and a pair of headwalls and a column at each of the corners of the ready-formed tray;
gluing of the columns;
shaping the columns;
gluing the side walls and the headwalls;
folding the side walls and the headwalls;
gluing of the external part of the columns which will be in contact with the headwalls;
placing the side walls in vertical position;
placing a body inside the columns;
pressing the headwalls against the columns;
placing the reinforcing elements in unfolded position on the bottom of the tray;
folding the ready-shaped tray into its transporting position.
This method affords considerable precision in the gluing of all the parts of the tray, since the shaping is carried out in the definitive position and not in the folded position, as are currently manufactured all trays formed from cardboard sheets.
The method of the invention also permits the manufacturing of trays with no thickness limit. This is due to the shaping being carried out in their definitive position.
Preferably, after pressing the headwalls against the columns some tabs inserted between the column and the reinforcing element are folded inside the columns, and these will be inserted between the column and the reinforcing element in its definitive position.
If desired, before the gluing the zone to be glued can be treated, preferably by heating that zone, which will facilitate adhesion of the glue.